Hydrogel capsules have been used to encapsulate cells since they can allow facile diffusion of oxygen and nutrients to the cells. Such compositions have been developed as potential therapeutics for a range of diseases including type I diabetes, cancer, and neurodegenerative disorders such as Parkinson's.
Traditional processing of hydrogel particles, such as alginate particles, provides little control over the microstructure or size (diameter) of the capsules. When living cells are encapsulated in the particles, the diffusion of oxygen and nutrients is restricted by the presence of the thick hydrogel shell. Also, proliferation and fusion of cells are prohibited due to the lack of aqueous space.
Moreover, the preparation of such particles often involves the use of organic solvents. Such solvents are costly, toxic, flammable and harmful to the environment. Upon solidifying the dispersed phase to form the solid capsules, organic solvents must be extracted by repeated washing which is time consuming. Therefore, it is highly desirable to replace the organic solvents with all aqueous solute to avoid these tedious steps to remove the organic phases. In addition, when protein solutions are exposed to the oil phase, denaturation of proteins often occurs at the water-oil (w/o) interface, reducing the bioactivity of the proteins.
Recent approaches to produce core-shell hydrogel capsules without the need for organic solvents using miscible aqueous solutions typically resulted in leakage of the payload.
Therefore, there exists a need for improved methods for preparing hydrogel capsules, particularly capsules that prevent leakage of the payload to be encapsulated but allows for efficient passage of oxygen and other nutrients to facilitate cell growth/survival.